Cytotoxic T lymphocytes (CTLs) have been shown to recognize epitope peptides derived from the tumor-associated antigens (TAAs) found on the major histocompatibility complex (MHC) class I molecule, and then kill the tumor cells. Since the discovery of the melanoma antigen (MAGE) family, many other TAAs have been discovered through immunological approaches (NPL1: Boon T, Int J Cancer 1993 May 8, 54(2): 177-80; NPL2: Boon T & van der Bruggen P, J Exp Med 1996 Mar. 1, 183(3): 725-9). Some of these TAAs are currently undergoing clinical development as immunotherapeutic targets.
In several of these TAAs, epitope peptides that can be recognized by CTLs are identified and their application in immunotherapy for various types of cancer is anticipated (NPL3: Harris C C, J Natl Cancer Inst 1996 Oct. 16, 88(20): 1442-55; NPL4: Butterfield L H et al., Cancer Res 1999 Jul. 1, 59(13): 3134-42; NPL5: Vissers J L et al., Cancer Res 1999 Nov. 1, 59(21): 5554-9; NPL6: van der Burg S H et al., J Immunol 1996 May 1, 156(9) 3308-14; NPL7: Tanaka F et al., Cancer Res 1997 Oct. 15, 57(20): 4465-8; NPL8: Fujie T et al., Int J Cancer 1999 Jan. 18, 80(2): 169-72; NPL9: Kikuchi M et. al., Int J Cancer 1999 May 5, 81(3): 439-66; NPL10: Oiso M et al., Int J Cancer 1999 May 5, 81(3): 387-94). Until now, several clinical trials using these TAA-derived CTL epitope peptides have been reported. Unfortunately, many of these clinical trials show a low objective response rate (NPL11: Belli F et al., J Clin Oncol 2002 Oct. 15, 20(20): 4169-80; NPL12: Coulie P G et al., Immunol Rev 2002 October, 188: 33-42; NPL13: Rosenberg S A et al., Nat Med 2004 September, 10(9): 909-15). Therefore, there is still demand for identification of novel CTL epitopes that can be used in cancer immunotherapy.
KOC1 (insulin-like growth factor II mRNA binding protein 3 also described as IGF2BP3 or IMP-3; reference sequence: GeneBank Accession Number NM_006547.2 (SEQ ID NO: 109)) is identified as a gene up-regulated in lung cancer by gene expression profile analysis using a genome-wide cDNA microarray containing 23,040 genes (NPL14: Kikuchi T et al., Oncogene. 2003 Apr. 10; 22(14): 2192-205; PTL1: WO2004/031413). The KOC1 expression is observed to be up-regulated specifically in tumor cells in over 90% of lung cancer patients, but it is not expressed in other normal important organs except the testis and placenta. Further, it is shown that cell proliferation in KOC1-expressing cancer cell lines is suppressed as a result of down-regulation of the KOC1 expression by RNA interference.
Recently, KOC1-derived HLA-A24-restricted CTL epitope peptides (PTL2: WO2006/090810; NPL15: Suda T et al., Cancer Sci. 2007 November; 98(11): 1803-8) and HLA-A2-restricted CTL epitope peptides (PTL3: WO2011/067920; NPL16: Tomita Y et al., Cancer Sci. 2011 January; 102(1): 71-8) have been identified. These peptides are effective in cancer patients having the HLA-A24 type or HLA-A2 type, but cannot be expected to have effect on cancer patients who do not have these HLA types.